High voltage, high power concentric transmission line



A. P. BOCK 'ot; I; 1946.

HIGH VOLTAGE, HIGH PCWER CONCENTRIC TRANSMISSION LINE Filed March 9, 1944 I r4 4 I 0 /2 WITNESSES:

INVENTOR fish/6y PBOCK.

ATTORNEY Patented Oct. 1, 1946 HIGH VOLTAGE, HIGH POWER CONCENTRIC TRANSMISSION LINE Ashley P. Bock, Catonville, Md., assignor to Westinghouse Electric Corporation, East Pittsburgh. Pa., a corporation of Pennsylvania Application March 9, 1944, Serial No. 525,688

Claims.

My invention generally relates to a physical construction for electric transmission lines of a type comprising a hollow relatively outer conductor and an inner conductor insulatedly supported centrally inside of the outer conductor, usually axially thereof; but my invention more specifically relates to providing a concentric or co-axial transmission line or cable capable of transmitting alternating current of voltages and powers higher than that carried by conventional lines of the same general type, including those that rely upon insulating washers for supporting and spacing the inner conductor.

An important object of my invention is to provide a construction for a concentric transmission line having a substantial support for the inner conductor, which provides a longer and narrower insulation or creepage path therealong, between the two conductors, so as to decrease the possibility of breakdowns and fiashovers.

A further object of my invention is to provide a transmission line of the type described for carrying high voltage alternating current at relatively high power with comparatively low leakage losses.

Still another object of my invention is to provide a transmission line of the type described for carrying high voltage, high power alternating current at high frequencies, including those obtainable only through resonant-circuit tubeoscillator power sources.

It is a general object of my invention to provide a transmission line of a type described which can be quickly and accurately manufactured and assembled, and which is sturdy in construction.

Still another object of my invention is to provide a transmission line of the type described comprising an outer tubular conductor and an inner conductor which is accurately maintained concentrically therein, at various spaced points if necessary, by an easily applied means capable of being easily repaired or replaced.

Further advantages, features and details of my invention will be discernible from the following description thereof which is to be taken in conjunction with the accompanying drawing. In the drawing:

Figure 1 is a longitudinal view, partly in elevation and partly in section, of a part of a transmission line embodying my invention;

Fig. 2 is a transverse view, partly in section, with parts broken away, of the transmission line;

Fig. 3 is a sectional view taken along the line III-III of Fig. 1;

Fig. 4 is a view, similar to Fig. 1, showing a modification provided with closure caps for closing the holes in the outer conductor; and

Fig. 5 is a transverse view, partly in section, of a modified form of a transmission line embodying my invention.

Referring to Figs. 1 to 3, my invention is shown embodied in a portion of a transmission line com-' prising an elongated hollow outer conductor 2, an elongated tubular inner conductor 4, and a plurality of insulating support means for supporting the inner conductor concentrically inside the outer conductor, each of the insulating support means being indicated in its entirety by the reference numeral 6. The conductors comprise one or more sections of a circular metal pipe, with the inner conductor 4 having a transverse outer periphery which is considerably smaller than, but geometrically similar to, the transverse inner periphery of the outer conductor 2. Associated with each insulating supporting means 6 is a lower hole 8 and a diametrically opposite upper hole in in the otherwise circumferentially solid tubular wall l2 of the outer conductor 2.

Each insulating support means 6 comprises an insulator I4 passing through and clearing the edges of the Wall I2 at the lower hole 8; the insulator having an inner end [6 which is used to the position of the portion of the inner conductor which it contacts, and an outer end I8 at a significant distance outwardly from the outer conductor 2. The extreme outer portion of the outer end l8 of the insulator i fixed, or cemented, in a short seat or socket 20 of a metal plate 22 having a base 24 provided with apertures 26 on each side of the insulator l4, spaced therefrom. These apertures receive elongated bolts 28 which pass through a pair of apertures 30 in the outer conductor 2 on opposite sides of the lower hole 8. The aperture 26 and the associated apertures 30 are preferably spaced the same distance apart. In the embodiment disclosed two apertures are provided in the plate 22 and two associated apertures in the outer conductor 2 for each insulating support means 6. Spacers 32 either metal or insulating tubes, depending on cost and on physical and electrical requirements, encompass each bolt for fixing the distance between the plate 22 and the nearest points of the outer conductor 2. Nuts 34 are tightenable on the bolts 28 for securing the plate 22 against the spacers 32.

For fastening the inner conductor 4 to the inner end l6 of the insulator, the latter may be provided with a pair of threaded holes for receiving a small clamping means which closely surrounds the inner conductor 3. and comprises a pair of screws 36 passing through a clamping bar 38, the screws being tightenable in the threaded holes of the insulator. The upper hole I6 permits ready access to the screws 36.

Obviously, by controlling the dimensions of the lower hole, the insulator, the bas plate and the spacers, the inner conductor can be accurately positioned inside the outer conductor. If for any reason an insulator should fail, become defective or otherwise require replacement, all that is necessary for repair is to loosen and remove the screws 33 and clamping 'bar 38 and then loosen the nuts 34 of the bolts 28 so that a plate 22 with a defective insulator thereon can be replaced with another plate and insulator; although it is obvious that the insulator 1B can be screw fitted or otherwise replaceably secured in the socket 20, if desired.

The bolts 28 and the spacers 32 can be made of any desired length. For placing long bolts in position, if they cannot be passed upwardly through the lower hole 8 or downwardly through the upper hole III, the apertures 30 in outer conductor 2 can be mad in the form of slots opening at the lower hole 3, or the heads of the bolts maybe separate nuts screwable on the associated ends of the bolts.

As illustrative only of my invention, and not by way of limitation, a practical embodiment of my invention which carried 400 kw. at a voltage of '7.,'500 volts and a frequency of 150,000 cycles comprised an outer conductor of 4 inch copper pipe, and an inner conductor of inch copper pipe. The upper hole, th lower hole and the insulator were on a common line of centers, having diameters which were, respectively, 1 inch, 1% inch and '1 inch; the insulated length of the insulator, between the inner conductor 4 and the plate 22, being 5 inches. This means, of course, that the insulator cleared th lower hole by about A; of an inch around its circumference and that the minimum creepage distance from the inner conductor, at one potential, to the other conductor, at a different potential, was about '5 inches along the surface of the insulator.

The number of and spacing between insulating support means is obviously optional, but may, in some cases, be dependent upon the required electrical characteristics of the transmission line. My invention has been applied to lines in excess of 25 feet in .length. Similarly the number of securing bolts, such as bolts 28, which secure and position the insulator, and the location of the apertures, such as 39, in the outer conductor for receiving the bolts, are optional, depending, sometimes, on the degree of rigidity desired.

If desired the lower holes 8 and the upper holes l may be provided with a metallic cup or cover so that the electrical fields are substantially entirely confined inside the outer conductor. Fig. 4 .shows caps 40 and 42 applied for covering the upper and lower holes, the lower cap encompassing theinsulating supporting means.

Fig. 5 shows afurther modification which does not require an upper hole. In this embodiment the insulating supporting means comprises a stiff narrow bracket band shaped and detachably, or otherwise, fastened to a convenient place on the outer conductor 2, the bracket band having a depending portion comprising legs 52 and a connecting base-bar 54 to which the plate 22 may be detachably secured. Fig. 5 further difiers from the prior embodiment in utilizing a clip 55 which snaps on and ofi the inner conductor 4.

Because of the increased insulating distance along the insulating support means 6 for the inner conductor of the transmission line built in accordance with my invention, the use of inert gases, with gastight seals, is not necessary for providing adequate insulation. If the inner conductor is made hollow it may be liquid cooled .ior carrying high values of current.

' While I have described my invention'in forms which I now prefer, it is obvious that many modifications and different embodiments may be made utilizing the principles and teaching of my invention.

'I claim as my invention:

1. An alternating-current transmission line comprising an outer hollow tubular conductor having a hole in its tubular wall, an inner tubular conductor spanning said hole, means for supporting said inner conductor inside and insulated from .said outer conductor, said means comprising an insulator device passing through and clearing said hole, means for securing an outer end of said insulator .device to said outer conductor, said insulator device having an'inner end at said inner conductor, and clamping means on said inner insulator end, for securing and positioning the portion of said inner conductor associated therewith, said clamping means compris ing a clamping member releasably clamping the conductor to said insulator device.

2. An alternating-current transmission line comprising an outer hollow tubular conductor having a hole in its tubular well, an inner tubular conductor spanning said hole, means for supporting said inner conductor inside and insulated from said outer conductor, said means comprising an insulator device passing through and clearing said hole, means for securing an outer end of said insulator device to said outer conductor, said insulator device having an inner end at said inner conductor, and means for relatively fixing together said inner end of said insulator device and the portion of said inner conductor associated therewith; the last said means comprising a releasable part attached to Said insulator device operable for releasing said insulator device from said inner conductor, said outer conductor having a hole in proximity to said releasable part for permitting access thereto.

3. A concentric electric transmission line comprising an elongated outer hollow tubular conductor having a hole in its tubular wall, an elongated inner conductor spanning said hole, -an insulator means projecting through said hole, a band secured to said outer conductor for supporting said insulator means, the inner end of said insulator means being at said inner conductor, and means for securing said inner end to said inner conductor.

4. A concentric electric transmission line comprising an elongated outer hollow tubular conductor having a hole in its tubular wall, an elongated inner conductor spanning said hole, an insulator extending through and clearing said hole, having an end at said inner conductor and an end outward from said outer conductor, and means for detachably securing said ends of insulator to said conductors for insulatedly supporting said inner conductor inside said outer conductor, said means comprising separable means on the inner end of said insulator.

5. The invention of claim '2 characterized by including a metallic cap for the last said hole, said cap generally following the shape of said outer conductor.

ASHLEY P. BOCK. 

